1. Field of the Invention
The present invention relates to an antenna device, and particularly to an antenna device with a grounding structure.
2. The Related Art
Wireless communication devices, such as cellular phones, notebook computers, electronic appliances, and the like, are normally installed with an antenna that servers as a medium for transmission and reception of electromagnetic signals. The antenna may be mounted outside or in the device. In general use, the antenna is built-in the device to save space and increase convenience. A conventional antenna device is illustrated in FIG. 7 and includes a printed circuit board 92 and an antenna 94. The antenna 94 with a grounding point 95 and a feed-in point 96 is arranged close to the surface of the printed circuit board 92. The grounding point 95 and the feed-in point 96 are electrically coupled with the printed circuit board 92. A metal layer (not labeled) provided on the surface of the printed circuit board 92 functions as a ground for the antenna 94.
However, as the wireless communication devices tend to be miniaturized, the size of the printed circuit board accordingly becomes smaller and smaller. The area of the printed circuit board used for functioning as the ground is restricted. Reduction of the area of the ground weakens the performance of transmitting and receiving electromagnetic signals of the antenna device.